The present invention relates in general to means for controlling the bounce or rebound motion of an armature of a solenoid valve and finds use in high performance fuel injectors.
In general, a solenoid valve comprises an armature movable between a first and second position. The extremes of the these first and second positions are often defined by mechanical stops. Armatures, as is known in the art, are moved in one direction by a electro-magnetic force generated by a coil of wire and often moved in the opposite direction by a return spring. When the armature impacts a stop it bounces. Bounce or rebound is detrimental especially if the solenoid is to be used as a positioning device because desired position cannot be maintained, or if the solenoid is incorporated within a fuel injector wherein when the armature moves toward or away from a valve seat due to bounce or rebound more or less fuel, as the case may be, will be ejected from the fuel injector. The bouncing continues until the hystersis losses in the armature and/or stop finally cause the armature to come to rest. As can be seen, the bounce of an armature effects the operation of a fuel injector by: prolonging or shorting the duration of injection, causing non-linearality in calibration, excessive wear about the valve seat area, poor and variable atomization of the ejected fuel, a lack of repeatability in the operation of the injector over its useful life and a cycle-to-cycle variation in the performance of the injector.
In view of the above it is primary object of the present invention to provide means for damping the motion of an armature to lesson and/or totally eliminate bounce. A further object of the invention is to eliminate bounce through the use of an energy absorbing device.
Accordingly the present invention comprises: means, attached to and movable with the armature for damping the motion of an armature by dissipating energy from a collision of the armature with the stop means. In one embodiment of the invention the damping means comprises a dynamic energy absorber or damper including an elastomeric sheath positioned about the armature and a weight attached to the outer surface of the sheath. In another embodiment of the invention the absorber comprises a plurality elastomeric rings positioned about and axially spaced along the armature and a weight, compressively loaded onto the O-rings. In this embodiment of the invention the weight comprises two semi-cylindrical sections, opposingly positioned onto the O-rings and wherein the spring loading is derived from a plurality of spring rings received about the semi-cylindrical sections. In another embodiment the absorber comprises a spring loaded weight which rubs upon the exterior of an armature to dissipate energy.